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Why do the system measurements deviate from manual measurements?

Common misconceptions when comparing manual measurements, e.g. taken with a measurement tape, to automatic measurements.

Deviations can have several issues:

  • Technical: Damaged sensors
  • Calibration: The calibration may be off due to physical impact (e.g. forklift), manual modifications to the system or a normal deviation over time
  • Bad illumination: Intense sunlight or other infrared light sources may interfer with the cameras
  • Unsuitable reference measurements

 

This article provides details on the last bullet point: unsuitable reference measurements.

Commonly the dimensions of boxes or pallets are measured along their edges. This approach is suitable for perfect cuboids, but usually not applicable for real logistics scenarios as pallets and boxes:

  • Cardboard boxes are no perfect cuboids. They may be longer on one side than on the other side. See example 3 and 4 below.
  • Items get damaged during transport. Consequently cardboard or tape pieces may stick out.
  • Boxes may become bulgy when packed very tightly, especially with heavy items. See example 2 below.
  • The center of a box may be higher than the corners as the top lids oftentimes stick out by themselves. This is even more severe if the contents have been "forced" into the box. See example 1 below.
  • Boxes may deform when tightly wrapped with strapping tape.
  • Pallets that carry several smaller boxes may be packed suboptimal, such that some boxes stick out.


Example 1: Irregular Box with Hump

  • The left corner (1) of the box is taller than the right corner (2). 
  • The section marked with (3) is higher than the box corners. This "hump" is commonly ignored when measuring with a tape measure.

Example 2: Bulgy Box

  • (1) The box is bulgy, especially on the left and right side (compare the red straight line with the box contour).
  • (2) and (3) Additionally, the side face has protrusions which are not considered when using a tape measure to measure along the top edges.

 

Example 3: Non-flat surface 

Screenshot 2024-02-07 102536 Side view of an imperfect box with non-flat bottom and top surfaces. The red arrows indicate the MetriX measurements.

Screenshot 2024-02-07 103843

MetriXFreight always measures the minimum enclosing cuboid of an object. As a box usually is not an ideal cuboid, this can lead to differences between hand measurements and MetriXFreight measurements that might seem unintuitive.

Example 4: Sheared Box

Screenshot 2024-02-07 102550 Side view of an imperfect box with sheared sides. The red arrows indicate the MetriX measurements.

Screenshot 2024-02-07 103902

 

As you can see, manual meassurements can be quite tricky. Irregularities of parcels might be hard to see for the human eye.

If you are still unsure if your system is meassuring correctly, try calibrating your device.